Book Review | Randomness in Evolution

The most striking illustration that encapsulates Bonner’s arguments is a diagram that shows as organisms become larger over time, they are constrained to an ever greater degree by the forces of natural selection. Photo: Ramesh Pathania/Mint

Updated: Thu, Jun 20 2013. 04 33 PM IST

Among the best science books ever was the 1987-Pulitzer-winning Chaos by James Gleick that dealt with the ideas of randomness and chaos. That small invisible factors could stealthily build up over time and upset ostensibly-predictable systems such the weatherman’s forecast of a sunny day is the essence of understanding the import of chaotic systems. However, Gleick’s work was of course a literary collage of many years of research in fields as diverse as information theory and population genetics, where researchers had been mathematically modelling the evolution of life. Though enormously successful, there was always the nagging problem of delineating the role of chance, or randomness, in directing the diversity of life.

In Randomness in Evolution, the eminent Princeton biologist, John Tyler Bonner argues that randomness plays a stellar role and lives unfairly in the penumbra of natural selection. Charles Darwin’s seminal insight: that everything from bacteria to blue whales came because of gradual, invisible, continuing and, most importantly, purposeless mutations. The most useful of those that survived nature’s winnowing, were passed on over generations and man himself was no special creature of God and “…bore in his bodily frame the indelible stamp of his lowly origin…”

During the first half of the 20th century, after concepts such as genes and DNA were well established and validated Darwin, there continued to be two key thorny issues: how does purposeless natural selection explain the variation within a species—what makes cats and tigers so different though they are part of the same extended family—and whether natural selection works as potently on blue whales as much as say slime molds, a kind of amoeba that Tyler has spent more than half his professional life studying.

The most striking illustration that encapsulates Bonner’s arguments is a diagram that shows as organisms become larger over time, they are constrained to an ever greater degree by the forces of natural selection. But go down—to the realm of the microbes and diatoms—it’s quite possible to observe a much wider range of species.

Species become bigger by accumulating greater numbers of cells that are in turn co-opted into larger networks that perform specific functions to aid mating, foraging and just getting by each day. Bigger cell networks and limited resources mean greater competition within cell-groups (organisms) and leading to the well known survival-of-the-fittest competition. This would mean bigger organisms are less likely to survive if subject to the whims of random mutations.

The trouble with Bonner’s contentions is that though he does give some evidence to prove his point, it is simply not enough. It is unclear how, in any reasonable way, can someone point to a particular species and cleave the influence of natural selection—in other words, by the effects of environment on organisms—from randomness. Just as one cannot convincingly prove how much of a man is nature and how much nurture and because his examples are mostly restricted to the arcane world of the microbial—apart from an aside on the division of labour in ants and honeybees. It is unlikely that many, who are not professional biologists, will be significantly convinced of the importance of randomness.

Bonner’s deserves credit for many insightful observations, such as how the great diversity of microbial forms within even a small patch of soil must point to explanations other than those of a predatory natural selection. But even if randomness is under-appreciated, why should that be a big deal? Nowhere does Bonner explain how a better appreciation of randomness could clarify existing ideas of evolution and ecological variety. Bonner himself acknowledges that “natural selection remains the master...” in the evolutionary game and then for him to later on claim that “randomness is necessary to counteract the tremendous power of natural selection that to some degree blinds our vision…” is more confusing than controversial.